Xxhsum improved help

[walterdejong]

some fixes to the help message for xxhsum

• show help message for option --files-from (it was undocumented)
• align the help under "Options" with the column under "Advanced"

[Cyan4973]

I like the proposed update.
But the following statement :

the program treats no filename as an error (XSUM_badusage) so the original help message was incorrect.

looks incorrect to me.

for example :

echo hello | xxhsum
e4c191d091bd8853  stdin

as one can see, no input is provided, so xxhsum uses stdin.

Not to be confused with :

xxhsum
Wrong parameters

In this case, there isn't even a stdin, so it fails.

[walterdejong]

I was talking about this behavior:

$ ./xxhsum --files-from
Wrong parameters

xxhsum 0.8.3 by Yann Collet 
Create or verify checksums using fast non-cryptographic algorithm xxHash 

Usage: xxhsum [options] [files] 

When no filename provided or when '-' is provided, uses stdin as input. 

[Cyan4973]

It also works :

echo README.md | xxhsum --files-from
021486ed356c9bbc  README.md

or even:

ls | xxhsum --files-from

b250f752fe46f746  appveyor.yml
1e31975f81f9b9cc  CHANGELOG
1672809750935c3b  Doxyfile
fabee07a1ea250e5  Doxyfile-internal
a14d327d280a4f5d  libxxhash.a
c0c8b0b129cdb72d  libxxhash.pc.in
f2738649c137765d  libxxhash.so
f2738649c137765d  libxxhash.so.0
f2738649c137765d  libxxhash.so.0.8.3
4a2ace65fa00bd3e  LICENSE
c5f936d59e9edff2  Makefile
021486ed356c9bbc  README.md
(...)

Same idea here :

xxhsum --files-from
Wrong parameters

fails because there isn't any input at all, not even stdin.

[walterdejong]

Aha, I see your reasoning.